Use of Genomics for Transfusion Therapy Management in Patients with Sickle Cell Disease

Abstract 2324

A genomic approach to blood group typing is now possible and high-throughput automated platforms have been developed to test for numerous blood group antigens in a single assay. These methods are reproducible and highly correlated with RBC serologic phenotype. We routinely perform a complete RBC phenotype for clinically significant minor red cell antigens on pre-transfusion samples from patients with sickle cell disease, and we antigen match patients for C, E, and K for transfusion.

In this study we compared the historic serologic typing with that predicted from DNA testing for clinically significant antigens in 114 samples from chronically transfused patients with SCD to determine concordance and to evaluate the clinical utility of genotyping for the management of transfusion therapy.

Serologic typing was performed by standard methods with licensed commercial reagents. DNA was isolated from WBCs, and minor antigen genotyping was performed with HEA (human erythrocyte antigen) BeadChip (BioArray, Inc). RH genotyping was by a combination of methods including PCR-RFLP, AS-PCR, exon-specific amplification and sequencing, and, for some, Rh-cDNA amplification and sequencing.

Comparison of serologic typing with DNA-based testing for thirteen blood group antigens, CcEe, Fya/b, K, Jka/b, MN and Ss, in 114 samples found 8 discrepancies in 1,482 antigens analyzed, for 99.5 % concordance. Discrepancies were in several systems (C, Fy, Ss, and M), and at least one has been confirmed to be a serologic recording error. All are under investigation.

DNA-based testing for RH found 54 of 114 patients inherited variant RHD alleles; many also had conventional RHD in trans. Sixteen patients had made anti-D, despite typing as D+. Ten of 35 patients (∼30%) whose RBCs typed as C+ had a hybrid allele encoding variant C antigen. Five had made anti-C, which prompted us to change our protocol so patients with variant C by DNA testing are transfused on a C- protocol. DNA testing found a large amount of diversity in ce-alleles in this population. Seventy-two of 114 patients carried at least one of nine different variant ce-alleles. Ten patients had made anti-e, despite typing as e+, and were homozygous for variant ce-alleles. In total, 49/114 patients with SCD were homozygous for variant RH alleles and were not truly Rh matched for D, C and e antigens by serology.

Similar to the way in which HLA typing by DNA has revolutionized bone marrow transplantation by providing a superior alternative to serological testing, we find that minor blood group antigen typing by DNA improves efficiency, reduces cost, and expands antigen matching, especially in the Rh system. Continuing studies are needed to identify more precisely which variant alleles are associated with clinically significant antibody production to improve antigen matching for patients with sickle cell disease.